Many intermediate bus converters (IBC) and almost all adaptive bus converters (ABC) supplying DC power at power levels above 200 W and with a size of ⅛ brick or larger have controllers on the secondary side of the converter due to system communication and pre-bias requirements. Due to physical size and cost restrictions however, bulky primary current transformers and expensive isolated linear voltage transceivers are rarely used. Thus, how to implement digital control without direct primary voltage and current sensing becomes a concern. Most existing solutions utilize an extra bias transformer winding and a sample-hold circuit to sense primary voltage. The voltage signal has to be filtered and even amplified before feeding to a digital controller. It usually requires several switching cycles for external circuits to respond while converter sensing and firmware interrupts may require additional time to process the voltage information before a modulated duty cycle can be adjusted. The slow signal sensing and control response does not allow the converters to have limited output voltage disturbances when input voltage surges occur. Too great of an output voltage disturbance can cause the converters to shut down.